After a DNS lookup failure, assume there is no internet connection.

Glyn Normington · nebhale · commit 3620bb98ba87 · 2014-02-26T07:52:22.000Z
This can occur in two places. If it occurs when sending a HEAD request
against a version of an item in the application cache, mark the
internet as unavailable and use the cached item. If it occurs when
downloading an item, mark the internet as unavailable and look for the
item in the buildpack cache.

[#66409480]
diff --git a/lib/java_buildpack/util/cache/download_cache.rb b/lib/java_buildpack/util/cache/download_cache.rb
@@ -147,6 +147,9 @@ def download(mutable_file_cache, uri)
           fail(InferredNetworkFailure, "Unexpected HTTP response: #{response_code}")
         end
       end
+    rescue => ex
+      handle_failure(ex, 1, 1) {}
+      false
     end
 
     def file_cache(uri)
@@ -169,6 +172,7 @@ def http_options(rich_uri)
     end
 
     def issue_http_request(request, uri, &block)
+      @logger.debug { "HTTP.start(#{start_parameters(uri)})" }
       Net::HTTP.start(*start_parameters(uri)) do |http|
         retry_http_request(http, request, &block)
       end
@@ -256,6 +260,9 @@ def up_to_date_check(immutable_file_cache, uri)
         end
       end
       use_cache
+    rescue => ex
+      handle_failure(ex, 1, 1) {}
+      false
     end
 
     def use_ssl?(rich_uri)
diff --git a/lib/java_buildpack/util/cache/internet_availability.rb b/lib/java_buildpack/util/cache/internet_availability.rb
@@ -62,7 +62,7 @@ def internet_available
       #
       # @param [String] reason a diagnostic which indicates why the internet should be deemed unavailable
       def internet_unavailable(reason)
-        logger.error { reason } if internet_availability_stored?
+        logger.error { "Internet unavailable: #{reason}. Buildpack cache will be used." } if internet_availability_stored?
         store_internet_availability false
       end
 
diff --git a/spec/java_buildpack/util/cache/download_cache_spec.rb b/spec/java_buildpack/util/cache/download_cache_spec.rb
@@ -293,9 +293,31 @@
     expect_file_deleted 'lock'
   end
 
+  it 'should use the cached copy if the HEAD request cannot be made because, for example, the DNS is unavailable' do
+    allow(Net::HTTP).to receive(:start).and_raise('DNS error')
+
+    touch app_dir, 'cached', 'foo-cached'
+    touch app_dir, 'etag', 'foo-etag'
+    touch app_dir, 'last_modified', 'foo-last-modified'
+
+    download_cache.get('http://foo-uri/') do |file|
+      expect(file.read).to eq('foo-cached')
+    end
+  end
+
   context do
     include_context 'buildpack_cache_helper'
 
+    it 'should use the buildpack cache if the download cannot be done because, for example, the DNS is unavailable' do
+      allow(Net::HTTP).to receive(:start).and_raise('DNS error')
+
+      touch java_buildpack_cache_dir, 'cached', 'foo-stashed'
+
+      download_cache.get('http://foo-uri/') do |file|
+        expect(file.read).to eq('foo-stashed')
+      end
+    end
+
     it 'should use the buildpack cache if the download cannot be completed' do
       stub_request(:get, 'http://foo-uri/').to_raise(SocketError)
 

Original file line number	Diff line number	Diff line change
`@@ -62,7 +62,7 @@ def internet_available`
`62`	`62`	`#`
`63`	`63`	`# @param [String] reason a diagnostic which indicates why the internet should be deemed unavailable`
`64`	`64`	`def internet_unavailable(reason)`
`65`		`- logger.error { reason } if internet_availability_stored?`
	`65`	`+ logger.error { "Internet unavailable: #{reason}. Buildpack cache will be used." } if internet_availability_stored?`
`66`	`66`	`store_internet_availability false`
`67`	`67`	`end`
`68`	`68`